Lithographic projection exposure apparatuses, such as are used for producing integrated electrical circuits and other microstructured components, image structures contained in a reticle onto a light-sensitive layer generally in a reduced manner, which light-sensitive layer can be applied e.g. on a silicon wafer. One exemplary construction for such a projection exposure apparatus is known from DE 10302664 A1.
One of the major aims in the development of projection exposure apparatuses consists in being able to lithographically define structures with increasingly smaller dimensions on the light-sensitive layer. The higher integration densities possible as a result for the microstructured components produced with the aid of such apparatuses generally considerably increase the performance of the components. The production of particularly small structure sizes presupposes a high resolution capability of the projection systems used. Since the resolution capability of the projection systems is inversely proportional to the wavelength of the projection light, successive product generations of such projection exposure apparatuses use projection light having ever shorter wavelengths. Current developments are directed to the development of projection exposure apparatuses which use projection light having a wavelength in the extreme ultraviolet spectral range (EUV). In particular wavelengths of between 1 nm and 30 nm, and in particular the wavelength of 13.5 nm, are taken into consideration in this case.
For guiding the light emitted by a suitable light source in the beam path of a projection system it is possible to use mirror arrangements including a plurality of mirror arrays, wherein each mirror array has a multiplicity of closely adjacent, relatively small-area mirror facets whose optical alignment is variable in a controlled manner in each case by themselves or in defined groups. The mirror facets can heat up greatly in the context of operation of a corresponding projection system owing to the light which impinges on the mirror facets and is partly absorbed here, and also as a result of the inherent power consumption of the mirror adjusting devices assigned to the respective mirror facets. The heating can lead to undesirable effects such as e.g., deformations of the mirror arrays, of the mirror facets or of the entire mirror system. Moreover, high temperatures can damage the sensitive reflective layers of the mirror system. In this case, DE 102013205214 A1 discloses dissipating the heat arising in the region surrounding the mirror facets by means of a gas flow.